High efficient anti-Stokes signal conversion in photonic crystal fiber

Abstract

The anti-Stokes frequency conversion based on four-wave mixing (FWM) has been widely used to generate short-wavelength radiation for high resolution imaging, direct excitation of electronic molecular transitions, and so on. For achieving more effective anti-Stokes conversion, we use the Ti: sapphire laser with a central wavelength of 810 nm and a pulse width of 120 fs as a pump source, and the degenerated FWMs of the higher mode and the fundamental mode are achieved respectively in 0.5 m long and 3 m long photonic crystal fibers (PCFs) with a zero dispersion wavelength of fundamental mode around 820nm in our experiment. The anti-Stokes signals around 560nm are generated efficiently at the fundamental phase matching. The maximum power ratios of anti-Stokes signal at 562 nm to the residual pump component and the Stokes signal are above 33:1 and 25:1, respectively. The maximum conversion efficiencies are achieved to be up to 48% and 34% in theory and experiment, respectively. And then the variation laws of the phase matching and the output spectrum with pump power, wavelength and the fiber length are obtained and the discrepancy between theoretical and experimental results is analyzed. Moreover, the effects of more factors on experimental results are discussed.